The present invention relates generally to a dynamic control system for an automotive vehicle, and more particularly, to a system of enhancing the trailerability of a vehicle using a yaw stability control system.
Dynamic control systems for automotive vehicles have recently begun to be offered on various products. Dynamic control systems typically control the yaw of the vehicle by controlling the braking effort at the various wheels of the vehicle. Yaw control systems typically compare the desired direction of the vehicle based upon the steering wheel angle and the direction of travel. By regulating the amount of braking at each corner of the vehicle, the desired direction of travel may be maintained.
Such systems typically include the capability of controlling one wheel or multiple wheels individually. That is, the vehicle wheels may be braked individually. Individual braking is typically performed on a demand basis for a relatively short time to stabilize the vehicle. Further, a vehicle wheel may be provided with a different torque than the other wheels. This may be desirable to perform certain controls in dynamic stability control systems.
Large vehicles such as fullsize sport utility vehicles, pickup trucks, and heavy duty trucks have a large turning radius. Such vehicles may be used to pull trailers. It would be desirable to improve the turning characteristics of these vehicles by reducing the turning radius. It would also be desirable to improve the trailering characteristics of a vehicle.
One system that is known to improve the turning characteristics of the vehicle is a four wheel steer system. By steering the rear wheels in the opposite direction of the front wheels in low speed, the turning radius of the vehicle is reduced. Four wheel steering is also capable of improving the trailerability of a vehicle in high speed. One drawback to such a system is that the system adds another steering actuator to the vehicle. This increases the cost, complexity, warranty, maintenance costs and weight of the vehicle. In contrast, it is typically the objective today to reduce the cost and weight of vehicles.
It would therefore be desirable to improve the turning capability and trailerability of vehicles without incurring the drawbacks of a four wheel steering system.